SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0317 PM CDT Mon Jun 13 2022
Valid 132000Z - 141200Z
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF FAR SOUTHERN LOWER MICHIGAN INTO NORTHEAST INDIANA AND WESTERN
OHIO...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
THE NORTHERN PLAINS...
...SUMMARY...
Scattered severe thunderstorms are expected across parts of the
northern Plains, and from portions of the Midwest into the Great
Lakes and Ohio Valley. Large hail, damaging winds, and a few
tornadoes are possible. Some of the winds could be significantly
severe (75+ mph) across parts of the Midwest/Ohio Valley this
afternoon and tonight.
...20Z Update...
Portions of the Ohio Valley have been upgraded to a Moderate Risk
for the anticipation of a highly organized MCS/possible Derecho
developing from a supercell structure across southern WI. Despite
the lack of agreement in high-resolution guidance, this supercell is
traversing a strong buoyancy gradient (with extreme MLCAPE values
exceeding 5000 J/kg noted in the OH Valley). In addition, 40+ kts of
effective bulk shear are also present along the buoyancy gradient,
which expands across a long west-east corridor over northern
portions of the OH Valley. Expectations are for this supercell
(which already shows an intense RFD surge per latest KMKX radar
data) to eventually become more outflow dominant, generating a
strong cold pool preceded by the extreme instability. Upscale growth
with the cold pool would support an expanding MCS traversing a
CAPE/shear parameter space typically associated with bow
echoes/derechoes. In addition, multicells continue to percolate
across central IN amid an extremely unstable environment (i.e. 5000+
J/kg MLCAPE per 18Z mesoanalysis) and an appreciable severe wind
threat could develop with this cluster as well should upscale growth
occur.
A significant wind area has been added to portions of the Slight
Risk across portions of central into northern South Dakota. Here,
the potential exists for an HP supercell/short bowing segment to
manifest from earlier storms along or immediately behind the surface
cold front somewhere within the 03-06Z period (especially in the
12-18Z runs of the HRRR) and traverse an axis of high-end elevated
buoyancy (i.e. 4000 J/kg MUCAPE driven by 9 C/km deep-layer lapse
rates). Should this scenario unfold, 75+ mph gusts may occur in
addition to 2+ inch hail. Consideration was considered for an
upgrade to a Category 3/Enhanced. However, the localized
nature/expected limited coverage of the higher-end severe threat
precludes an upgrade. Please see MCD #1144 for short-term severe
concerns across the northern Plains.
..Squitieri.. 06/13/2022
.PREV DISCUSSION... /ISSUED 1204 PM CDT Mon Jun 13 2022/
...Midwest/Great Lakes...
A consequential potential for impactful storms exists today into
tonight across the region, potentially including long-lived/intense
MCS development, owing to a high degree of moisture and extreme
potential instability. However, short-term uncertainty remains high
regarding spatial details exists owing to a strong capping
inversion, along with guidance variability in terms of
timing/spatial differences.
Multiple MCVs, albeit generally weakening, are still readily
apparent at late morning across portions of Iowa/southern Minnesota
into western Wisconsin. Regional WSR-88D VWP data features notably
enhanced mid-level winds, particularly by mid-June standards, within
this same regional corridor (for example, 50-60 kt winds 3-6 km AGL
recently noted at KDMX/Des Moines).
12z upper-air analysis in conjunction with more contemporary GPS PW
values reflects a moisture-rich corridor particularly from eastern
Iowa and much of Illinois southeastward into southern Indiana. A
considerable elevated mixed layer extends east-northeastward atop
this moisture, highlighted by a 14.6 C temperature at 700 mb per 12z
ILX/Lincoln, IL observed sounding.
Given the notable mid-level warmth, storm development later this
afternoon into evening will tend to favor areas near/immediate cool
side of a northward-shifting warm front across the region. This
would favor development across southern Wisconsin into northern
Indiana/Lower Michigan and Ohio. One potential exception could be
across downstate areas of eastern Illinois into Indiana, where
glancing MCV-related ascent (reference ongoing mid-level convection
near/west of the Mississippi River this morning) could interact with
a very moist/unstable and weakly inhibited boundary layer downstream
highlighted by surface dewpoints generally in the upper 70s F.
Where storms do regionally develop, large hail and damaging winds
can be expected, along with at least some potential for tornadoes
with surface-based storms developing near/interacting with the warm
front.
An upgrade to Moderate Risk may still be warranted across parts of
the region (particularly Lower Michigan, northern Indiana and/or
Ohio) pending subsequent observational trends and increased
confidence in a preferred sub-regional corridor of intense storm
development.
...Dakotas...
Influenced by the approaching upstream upper trough, a surface low
is forecast to deepen over eastern Wyoming this afternoon while a
cold front moves across the northern Rockies and High Plains.
Thunderstorms are expected to form along the front by early evening
over western South Dakota/North Dakota and track northeastward.
Vertical shear profiles will be favorable for supercell storms
capable of all hazards, particularly along and on the immediate cool
side of the boundary.
...Southern/central High Plains...
Modest moisture and a hot/deeply mixed boundary layer could support
a few severe-caliber wind gusts if/where storms develop late this
afternoon/early evening.
...Maine...
Influenced by modest buoyancy and moderately strong winds aloft on
the periphery of an upper low over Quebec, a few strong to severe
thunderstorms may occur this afternoon across the region.
Read more CHECK UPDATE ZOOM GRAPHIC
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